oil pressure

AndyF said
I've found that it doesn't matter where you read the oil pressure. The reading will be the same at either end of the engine. I once hooked up three oil pressure gauges to a big block just to check it for myself. One was at the outlet of the pump, one was at the inlet to the block and the third was at the back of the block. All three read the same so I got rid of two of the gauges.

Thanks Andy! That would suggest very little loss of flow from the pump through the galleries.

famous bob said
wouldn`t the oil pressure relief valve opening sooner drop the oil pressure straight across the rpm range , because it would open
quicker ?

At lower rpms the pump shouldn't be pushing enough oil to push the relief open.
Changing relief spring should change the maximum pressure and volume.
Orange line represents a higher pressure relief.

If at 3000 rpm, the pump starts to push enough oil to crack open the relief, that's the rpm pressure will start to level off.
A high volume pump will open the relief at lower rpm - assuming same oil viscosity, bearing clearances etc